Temperature control system with signal



April 1951 c. H. DICKE 2,548,424

TEMPERATURE CONTROL SYSTEM WITH SIGNAL Filed March 13, 1946 5 Sheets-Sheet 1 2% /r- 4 j W +7 90 OFF mu 0mm INVENTOR 55 dfaarl lijirffe BY' 4&4 f. C.

l-)TTORNEY.S

April 10, 1951 c. H. DlCKE TEMPERATURE CONTROL SYSTEM WITH SIGNAL 5 Sheets-Sheet 2 Filed March 15, 1946 INVENTOR Karl flJZr/K,

flTTORNEYfi April 10, 1951 c. H. DICKE 2,548,424

TEMPERATURE CONTROL SYSTEM WITH SIGNAL Filed March 15, 1946 5 Sheets-Sheet 3 T 11mm 05 W 0N OFF INVENTOR ['arl if fl/r/fe BY 7 a M HTTORNEYj C. H. DICKE TEMPERATURE CONTROL SYSTEM WITH SIGNAL April 10, 1951 5 Sheets-Sheet 4 Filed March 13, 1946 UNC/IZZ N NTO far] E i Zita ATTORNEY .5

0N OFF April 10, 1951 c. H. DlCKE TEMPERATURE CONTROL SYSTEM WITH SIGNAL 5 Sheets-Sheet 5 Filed March 13, 1946 INVENTOR. ('arl ll. flit/(e arrow/5Y5 Patented Apr. 10, 1951 TEMPERATURE CONTROL SYSTEM WITH SIGNAL Carl H. Dicke, New Bremen, Ohio, assignor, by

mesne assignments, to Crown Controls Company, Inc., New Bremen, Ohio, a corporation of Ohio Application March 13, 1946, Serial No. 654,052

6 Claims.

This invention relates to temperature control systems and a thermostat for use therewith, and relates more particularly to such a system in which indicating means, such as a signal lamp, is provided, so constructed and arranged that it will be in signal-producing condition at all times when the heat supply controlling device, such as a damper regulator motor, gas valve, relay, or the like, is in increased-heat position.

An object is to provide such a system in which the efiectivity of the signal device, such as a lamp, is determined, not by the position of the heatsupply controlling device, such as a damper motor, but by the thermostat itself, whereby the Signal is effective not only after the increased heat-supply position of the heat-supply controlling device has been raised but even during the operation thereof.

Another object is to provide such a system so arranged that the signal will truly indicate the condition or approaching condition of the heat supply control device irrespective of whether the heat-supply controlling device, such as a damper motor, has been actuated in response to the call of the thermostat, the call of a limit switch, or the call of a basement switch.

Another object of the invention is to provide such a system in which the signal given during the time while the heat-supply controlling device is being actuated difiers from the type of signal given after the operation has been completed.

Another object is to provide such a device which is so arranged that operation of the temperature-adjusting means of the thermostat is ineffective to de-energize the signal lamp when the basement switch is on call, or when the lowlimit switch is on call.

Another object is to provide a room thermostat of improved construction especially adapted for use in such a system.

Other objects are to provide improved signal lamp mounting means, convenient and reliable adjustment means for such thermostats, convenient and reliable means for attaching the cover thereof, to provide effective signal-indicating means on the cover and to provide means to prevent dust collecting on the contacts.

Another object of the present invention is to provide a damper regulator motor designed to cooperate with the signal lamp of the present invention.

Further objects and advantages of this invention will be apparent from consideration of the specification as illustrated by the accompanying drawings of possible embodiments of the invention, in which drawings:

Fig. 1 illustrates a temperature control system showing more or less schematically a. thermostat embodying the signal means of the present invention connected to a heat supply controlling device, such as a damper regulator motor;

Fig. 2 is an elevational view of a room thermostat embodying the invention, the usual cover having been removed;

Fig. 3 is a rear elevational view of the structure of Fig. 2;

Fig. 4 is a cross-sectional view taken on the line 4-4 of Fig. 2;

Fig. 5 is a side view of the thermostat of Fig. 2 with the cover thereon, the cover being shown in generally vertical, longitudinal section, except that the upper part is shown in section taken to the right of the center of the instrument;

Fig. 5A is a fragmentary section of the base and cover;

Fig. 6 is a fragmentary vertical, longitudinal section of the thermostat shown in Fig. 5;

Fig. '7 illustrates a temperature control system showing more or less schematically a thermostat embodying the present invention connected to a heat-supply controlling device, such as a damper regulator motor, said damper motor being provided with the conventional on and oif basement switch, the system also including a high limit switch and a low limit switch connected between the thermostat and the damper motor;

Fig. 8 illustrates the present invention as used with a limit switch having a basement switch embodied therein;

Fig. 9 illustrates a temperature control system in which the heat-supply control device consists of a solenoid fuel valve or a relay;

Fig. 10 illustrates such a system in which a high limit switch is employed; and

Fig. 11 illustrates such a system in which a high limit and a low limit switch are provided.

Referring to said drawings, the letter T indicates generally a room thermostat and the letters DM indicate generally a damper motor. The thermostat comprises a thermal-responsive element, such as the coiled bi-metal'element II, carried by a bracket I2, which is connected through conductor I3b with terminal I3a, to which is connected conductor I3. It represents the on call contact, connected through conductor I5b with terminal I50. to which is connected conductor I5, and I6 represents the off call contact, connected through conductor I'Ib with terminal Ila, to which is connected conductor I1.

The heat supply control device may consist of a damper regulator motor of standard construc tion, or may comprise a relay for controlling an oil burner, or for controlling the operation of the motor of a stoker, or may be an electricallyoperated gas'valve. In the form shown, the heat supply control device consists of an electric motor 25 connected through suitable gearing (not shown) to drive, at a much reduced speed, the shaft 22, which carries cranks 23 and 24' for operating the draft and check dampers of a solidfuel heating plant. Usual or suitable commutating means are provided. As shown, this takes the form of a metal tube 25, shown indevelopment in dotted lines, carried for rotation by shaft 22. It is formed with two insulating areas 25a and 25b. Cooperating with said tube are four brushes 2?, 2?, 28 and 29. Brush 23is' connected through conductor to with motor 2!, the other side of which is connected through conductor 3| and terminal 32 to the secondary winding 33' of a transformer 34, whose primary winding 35 is connected to a suitable source of alternating current. The other side of the winding 33 is connected through terminal 36 and conductor 31 with brush 23 and with terminal 38, to which conductor i3 is connected. Brush 2! is connected through conductor 39 to on terminal 40, to which terminal is connected the conductor [5. Brush 29 is connected through conductor GI with the off terminal 42, to which is connected the conductor 51.

53 indicates a signal device,-p-referably a small electric lamp" which not only serves to indicate the condition of the heat supply controlling device, but also serves as a supplemental heat source for increasing the sensitivity of the thermostat, as will be described more fully hereinafter. Said lamp is connected through conductor with a terminal 52, to which is connected conductor 53, the other end of which is connected to terminal 32 of the damper motor and thus to that side of the transformer secondary which is directly connected through conductor 3| with the motor 2|. The other side of the lamp 5!] is connected through conductor 54 with the on call contact l4.

' Before describing the details of the thermostat, the functions and operation of the system itself, as shown in Fig. 1, will be described.

Fig. 1 shows the parts in position where the damper motor has moved to drafts on position in response to' the call of the thermostat T, due to an electrical connection between bi-metal element i i and contact I l. The operation of motor 2l has terminated as a result of the insulation 25a coming under brush 21. It will be noted, however, that a circuit is open from the transformer secondary 33, terminal 32, through conductor 53, terminal 52, conductor 5!, through lamp 53, conductor 54, on call contact l4, bimetal element ll, bracket I2, conductor I31), terminal i311, conductor [3, terminal 38, conductor 37, terminal 36 to the other side of the transformer secondary. This circuit is completed solely through the bi-metal element I! contacting the on call contact l4 and the lamp will, therefore, continue illuminated as long as the thermostat is in the position shown. This condition is quite independent of the commutating means in the damper motor. During this time heat from the lamp 53 is conducted to the bimetal element M and serves, together with a resulting rise in the temperature of the room, to cause the bi-metal element l i to move to the left. This operation is preferably of the snap action type, so that the bi-metal leaves the on call contact ill and immediately makes connection with the off call contact it. This breaks the circuit through lamp 5i] and causes it to be extinguished. The circuit is, however, completed from transformer secondary 33, terminal 32, con ductor 3!, through motor 2|, conductor 30, brush 26, metallic tube 25, brush 29, conductor 4|, terminal 52, conductor l7, terminal Ila, conductor lib, off call contact I6, bi-metal H, bracket l2, conductor 23b, terminal 13a, conductor I3, terminal 33, conductor 31, and terminal 36 to the other side of the transformer secondary. This energizes motor 2! and causes it to rotate shaft 22 to move the damper motor to drafts off position. As soon as the insulation 25a moves from under both brushes 2? and 23, the lamp 553 will be energized through the circuit comprising conductor 53, terminal 52, conductor 5|, lamp 5D, conductor 53, conductor I51), terminal IBa, conductor l5, terminal 40, conductor 39, brush 2?, metallic tube 25, brush 28, conductor 31, and terminal 36 back to the other side of the transformer secondary. This circuit will be maintained only until insulation 25b moves under brush 23 at the end of the operation to the drafts off position of the damper motor. With the transformer 34 of the size usually used, the voltage of its secondary winding 33 is considerably reduced, due to the current flowing through motor 2|. Therefore, while the lamp 50 is lluminated during the operation of the damper motor from the drafts on to the drafts off position, the lamp will not be fully illuminated, but only partially. The damper motor is now in the drafts 01f position and the lamp E0 is extinguished, due to the bi-metal element ii not being in contact with the on call contact I4.

If now, the temperature drops, or for any other reason bi-metal ii is moved from the off call contact 56 to the on call contact M, the lamp will be immediately illuminated through the circuit including bi-metal element H, as previously described. During the operation of the damper motor from drafts off to drafts on position, the lamp will be dimly illuminated, due to the voltage drop in the transformer secondary. However, at the end of the operation, the lamp will be illuminated brightly and will remain illuminated, thus signalling to the user that the damper motor is in drafts on position. During this time the heat radiated by lamp 5B affects bi-metal element H and causes it to move from on call contact it to the off call contact it earlier than it would do otherwise, so that the sensitivity of the thermostat is increased thereby. It will be noted also that when the motor 2! is operated to either the drafts off or the drafts on position, the lamp 50 will be illuminated dimly and thus signal to the user that a change in draft position is taking place. The novel system just described has the advantage that the illumination of the signal lamp 3'0 is controlled by the thermostat bi-metal itself and is independent of the particular type of commutator, if any, which may be present in the heat supply control device with which it is employed.

The thermostat The thermostat illustrated in Figs. 2 to 6, inelusive, comprises a base 60 formed of a suitable insulating material, preferably of molded plastic material, having a forward face 6! and shown as formed. with rim 32 extending rearwardly therefrom and being split near its upper end, as appears from Fig. 4, to receive a rivet 65 having a head 6511, against which bears a cupped spring washer 66d, the outer rim of which bears against the forked portion of member 64. The rivet 65 is carried by the adjusting lever 66, which overlies the shifting fork 54 and is pivoted by means of screw or rivet 6?. The adjusting lever has an outward extension 66a (see Fig. to which is attached the vertical extension 6617, carrying, in turn, the horizontal extension 660, which projects through the cover and provides a manually adjustable member which also serves as a pointer to indicate the setting of the instrument through the agency of the usual scale (not shown) on the front of the cover. The bracket I2 is provided with a projection l2a threadably receiving an adjusting screw 10, the head 10a of which bear against a projection 54a, forming part of the shiftin fork 64. Interposed between the members [2a and 64a is a coiled spring ll, tending to force said members apart. By turning screw 19, the position of the bracket 12 relative to the shifting fork 64 may be readily adjusted.

In the form shown, the upper end of the bimetal element H is provided with a contact rivet 15, which may conveniently serve to attach to the element ll a soft steel washer 76, serving as an armature for a permanent magnet 11 supported upon a contact bracket 18 by means of a rivet 19 of good contact material, one end of which comprises the on call contact l4, shown schematically in Fig. '1. The contact bracket 18 is attached to the base by means of rivet 18a. 89 indicates another contact bracket attached to the base by rivet 89a. It carries a contact screw 8i formed with a contact point I6, forming the off call contact 18 shown in Fig. 1.

The lamp 50 is conveniently supported by means of a spring clip 5!, which forms the conductor 5| shown in Fig. l. Said clip surrounds the lamp 50, which may be of the usual telephone signal lamp type and makes contact with the contact terminal 50a of the lamp. Contact with the other terminal 50b of the lamp is prevented by the insulating material 510.. The clip 5| is shown supported upon a metal post 51b by means of screw Sic. It is imbedded in the base 60 and receives at its other end the terminal screw 52, corresponding to the terminal 52 of Fig.1.

The other terminal 50b of the lamp is contacted by means of the conducting piece 54-, corresponding to the conductor 54 in Fig. l, which is provided with a contact finger 56a. bearing on lamp contact 50?), and is held in place by the rivet 18a,

and is, therefore, in electrical connection with the on call contact 14. It will, therefore, be seen that through the means shown, the lamp 50 is connected in the circuit in the manner indicated'schematically in Fig. 1,

It will also be seen that the lamp 59 may be readily replaced by removing the screw 5lc, whereupon the burned out lamp, together with its clip 5|, may be removed and replaced by another lamp and clip. The lamp, clip, and insulating material 5 l a will, therefore, form a separate article of manufacture.

The openings 85 in the base, preferably flared as at 85a, Serve to receive attachment screws for securing the thermostat base to a wall. For this purpose, the base is formed solid adjacent said holes, as indicated at 86 in Fig. 3. These lugs serve to support the pressure of the holding screws whereby distortion of the base is prevented. By referring to Fig. 3, it will be noted that rivet 18a, after passing through the base material, also passes through a terminal link 18b, which serves as a riveting washer. At its other end it is formed with a threaded opening to receive the terminal screw 15a. Similarly, rivet a is riveted through terminal link 80b, which carries the terminal screw l'la. Likewise, the pivot rivet 51 is riveted into terminal link 61b, which carries the terminal screw l3a. By referring to Figs. 2 and 5, it will be noted that the base 60 is formed adjacent the rivet 61 with a raised boss 61a against which the adjusting lever 66 bears. This provides clearance under the lever 66 to accommodate the forked lever 64.

Referring to Fig. 5, it will be noted that a cover 99 is provided. This serves to protect the mechanism and carries, in the usual manner, a thermometer tube 9| adjacent the thermometer scale 91a on the face of the cover. The cover is preferably of translucent material so that light from the lamp 55 may illuminate the cover generally. It is preferred, however, to provide a window 92 of suitable colored translucent plastic or glass to make the light from lamp 50 more readily visible. The upper end of the cover is provided with a preferably centrally located opening 94 (Fig. 6). Adjacent said opening a baflie 95 is preferably provided to shield the contact points from dust, which might otherwise settle thereon. The location of this bafile is indicated in dotted lines in Fig. 2. A corresponding opening or openings 96 are formed at the bottom of the cover. At least one of these openings, as shown at 96a, extends to the bottom of the cover to provide flexibility of the cover when applying or removing it from the base. The cover is held in place on the base by any suitable means, such as a small lug 91 (Fig. 5A) formed on the inside of the cover, which lug engages behind the shoulders 98 formed in the base. To facilitate application of the cover and to cause it to be sprung apart during application to the base, the base is preferably formed also with recesses 99, having inclined faces. During the application of the cover, the lugs 91 bear against the inclined faces 99, causing the cover to be spread apart. The lugs 9! thereupon spring in place behind the shoulders 98. The lugs 91 and the edge of the shoulders 98 are rounded so that it will be possible to withdraw the cover. By placing the recesses 98 at the extreme bottom of the base, the formation thereof presents no difficulties in the molding operation, since they may be formed by a corresponding extension on the mold. Similarly, the molding of the cover with lugs 91 thereon presents no difliculties, since the cover is sufficiently elastic to permit the lugs 91 to be forced out of corresponding recesses in the mold when the cover is stripped from the mold core.

Fig. 7 illustrates a temperature control system employing the thermostat of the present invention connected to a damper regulator motor provided with a basement switch, the system also including a high limit switch and a low limit switch of conventional construction connected between the thermostat and the damper motor. The same reference numerals have been employed as in the other figures, insofar as applicable, and a further description of the construction common to Figs. 1 and '7 will, therefore, not be necessary. The damper motor of Fig. '7 may be identical with the damper motor of Fig. 1, with the exception of the basement switch. This consists of a switch arm 31a pivoted at 311) to the brush 28. Its other end is normally connected with conductor 31, as

. shown. As indicated in dotted lines, switch arm 1? 37d may be swung away from conductor 31 and into contact with brush 29 and conductor 4|, as shown in dotted lines, or it may be swung in the other direction into contact with brush 2'! and conductor 39, as shown in dotted lines.

The high-low limit switch may be of conven: tional construction-.- It may consist, for example, of thermo r'espons'ive material, such as the bimetal IIlI, fixed to a supporting bracket I02 and attached at its other end to a shaft I03; carrying cam I04 provided with a proje'tioii I04d Mounted t6 one side of said arm is the lo\if-liinit contact blade I05, carried by bracket I06 and normally spring-pressed to the right against the contact" I I5; Opposite thereto is the on contact- I I 6.- On the other side of the cam is ahigh limit spring contact arm I01, carried by bracket I08 and normally s ring-pressed to the 1ert and Iigaging the contact in. Opposite thereto is the olf" centact H8. There are provided terminals I09, H and III to which are connectedcon ,ductors I5, I3 and I 1, respectively. There are also provided terminals I2, I it and H4 to which are connected respectively conductors I so, see and I112 which are connected respectively to the terminals 40', 38 and. 32 of the damper motor. The terminal I09 is connected to the terminal I I2 by conductor I 20' and it is also connected by conductor I-2I with contact lit. Terminal H0 is connected via conductor I22 with contact II'I. Terminal I I l is' connected via conductor I23 with ofi contact H 8 and oh terminal I It. 'rer-- m'in'a'l H3 is" connected via conductor i-24 to bracket I06. Bracket I08 is connected via conductor I26 withconta' c't H t, It will be noted that the parts are so connected that intl'ie positions of the parts shown a circuit is completed from ter' min'al I312 or the thermostat through conductor I3, terminal 0, conductor I 22', highlimi-t contact I I1, spring arm I01, bracket I08,- conductor I26; contact H5, spring arm I05, bracket I06 and conductor I2 1 to terminal I I3, to which is connected the conductor I30 which connects with terminal 38 on the damper motor. Likewise, conductor I7, which leads from terminal I'Ia on the th'ear'mostat, leads" to terminal I i Ig on the limit switch and thence connects through conductor I23 to terminal H4, which is connected through conductor lie with terminal 42 on the damper motor. Terminal [5d of the thermostat is connected via conductor I5 with terminal 09 on the limit: switch, wh'erefrom it is connected by means" o'f condu'ctor' I20 with terminal H 2 which is connected through conductor I50 with the tea minal 40 of the damper motor.

I It will be noted that with the limit switch in the position shown in Fig. 7, and the basement switch in the position there shown, the circuit as between the thermostat and damper motor is the same as in Fig; 1-. In other words, there is an electrical connection between the thermostat bi metal bracket I2 and the brush 28, andthr'oug'h conductor 37b to the transformer sec ondary terminal 36; Likewise, there is an elec-' trical connection from the thermostat on contact I4 to the damper motor on terminal 40 and bfush 21. This is effected through elm:- ductor I5b, thermostat terminal I5a, conductor I 5, limit switchterminal I09, conductor I20 to terminal H2, and through conductor I50", ter''- minal 40 and conductor 39 to brush 2?. 7

Likewise} as Fig. 1-, a circuit is established from the fofitco'ntact It of the thermostat to the "ofi terminal 42 of the damper motor and to the brush 29. This is effected through the conductor I 6, conductor I lb, thermostat terminal Ila, conductor I1, limit switch terminal I I I, conduo-tor I23, terminal I I4, conductor Il'c to damper motor terminal 42, conductor 4| and brush 29.

Likewise, (assuming the thermostat to be in the on call position) a circuit is established from the transformer secondary at the terminal 32, through conductor 53, the lamp 50, conductor 54; contact I4, bi-metal arm Ii, through consectors I31),- te'r-minal I3a, and conductor I3 to terminal IIO of the limit switch, and thence through conductor I22, contact II1, blade I01, bracket I08,- conductor I 26, contact H5, blade I05, bracket I06, conductor I24, terminal II 3, and conductor I30; terminal 38, conductor 31, easement switchblade 31a, brush 28, conductor 37b and terminal 36 toflthe other side of the trarisfor "r secondary. The lamp 550 will, therefore, remain illuminated while the bi-metal arm I'I remains incontact with the thermostat on call contact I4.

By following the circuits shown in Fig. 7, it will be notedthat the lamp 50 will always be illuminated whenever the damper motoris in-the" drafts on position, whether this be the result of the call of the room thermostat (circuit just described), or as a resultof the call of the base: ments'witch, or as a result of thecall of the low limit switch.- The eighteen possible conditions and the resultant action can be seen from the following table:

on calll...

runs,thenbright. Cant turn ofl light at thermo stat.

Same as 3.

Same'as 2.

- That these results are obtained will be readily apparent to those skilled in this art by tracing the circuit shown in Fig. '1. From said table it will be noted that the lamp always truly indicates the condition of the drafts, whether as a result of the call of the room thermostat, the basement switch, or thelimit switch. When the drafts are open, the lamp is illuminated and when the drafts are closed, the lamp is extinguished. Fur thermore, if the user should leave the basement switc in on call position, the lamp cannot be turned on at the thermostat. If the thermostat-adjusting pointer BBC is moved to alower temperature position so that the b-i-metal ll moves from on call contact M to 01f call contact 16, the lamp will remain illuminated. This is the condition represented by operations numbers 3 and 4 in the above table. Similarly, the light cannot be turned off at the thermostat at any time when the basement switch is left in on call position, irrespective of the position of the limit switch. Thus, even if the high limit switch is in ofi call position and the basement switch in .on call position (operation 9), the

lamp is illuminated and when the thermostat is then moved to 01f call position (operation 10), the condition of the lamp is not affected. The fact that the lamp cannot be turned off at the thermostat is therefore an indication to the user that the basement switch has been left in its open position. 9 p

- Fig. 8 illustrates a temperature control system employing the thermostat of the present invention connected to a damper motor not provided with a basement switch, the system however, including a high limit switch and a low limit switch of the type having a basement switch incorporated therein, such as the limit switch disclosed and claimed in the pending application of Allen A. Dicke, Jr., filed January 25, 1946, Serial No. 643,343, now Patent No. 2,504,010, dated April 11, 1950.

' The same reference numerals have been employed as in the preceding figures, insofar as applicable, and a further description of the material common to Fig. 8' and the earlier figures is therefore unnecessary. The thermostat and the damper motor of Fig. 8 may be identical with those shown in Fig. l. The high-low limit-basement switch comprises a casing 251 which houses the high limit switch, the low limit switch, and their operating means, as well as the basement switch.

252 represents any thermo-resp0nsive element, such as coiled bi-metal, one end of which is attached to an abutment member 253 and the other end of which is attached to a rotatable shaft 254, the other end of which is connected for rotating the cam-operating member 255. In accordance with usual construction, the shaft 254 is suitably housed .in a. rearwardly extendinjg tube which, in use, extends into the bonnet of a hot air furnace or the flue pipe of any type of furnace.

The high limit switch may consist essentially of a switch blade 256 supported on bracket 251, its free end beingbiased againstthe on contact 258. The arm 256 is sufliciently flexible so that when operating cam 255 is rotated so that its high point 255a strikes the arm 256, said arm is moved away from on contact 258 into engagement with the off contact 259.

The low limit switch is shown as consisting of a flexiblecontact blade 266 Supported by bracket 261 and normally engaging off contact 2653 but 10 it may be moved by extension-255a or the em to inove away from contact 2 69 into engagement with on contact 268. r

The basement switch consists essentially of a switch lever 21! pivoted at 212 and normally in electrical connection with contact button 213'. It may be moved in one direction so as to leave the contact 213 and engage the off contact button 214. Similarly, it may be moved in the other direction to engage the on contact button 215,

The housing 25l is shown provided with termi nals as follows 215a to'which conductor-I 5 is attached, 2 Ha to which conductor 13 'is attached, and 2 Hz: to which conductor 11 is'attached.

Similarly, the housing carries terminals 2466. connected through conductor I50 with terminal 46 on the motor, as well as terminal 236a which is connected through conductor [30 with terminal 38 on the -motor, and also terminal 242:; which, through conductor [10, is connected 'to terminal 42 on the motor. I

Internal connections are as shown, viz., terminal 215a is connected through conductor 2552 to the on contact 258 of the low limit switch, the on contact 215 of the basement switch, and the on terminal 245a, and thence through conductor I50 to the on terminal 49 of the motor. Terminal 213ais connected through conductor 21319 with the"off contact 269 of the lowlimit switch. Terminal 211a is connected through. conductor 2l1b to the we contact 25% of the high limit switch, to the officont act an er the basement switch, and to' the off terminal 24211 which, through conductor I10, is connected'to the off terminal 42 of the-motor.- The bracket 251 is connected to the contact 213' of the basement switch through conductor 261d. The-pivot 212 of the basement switch is connected threluelfi conductor 212a with the on contact of the high limit switch.-- The bracket251 'of the high limit switch is connectedthrough conductor 251a with the terminal 238a and thencethrough conductor I30 with the common terminal 38 of the motor. I

The thermostat T and the motor are shown in a position where an :on call operation has just been completed. The motor 2| and shaft 22 are stationary because oni brush 21 is standing on insulation 25a. Ifnow, the temperature to which the limit-switch bi-metal 252 is subjected rises to a certain extent, cam 255 will rotate counterclockwise until extension 255a thereon strikes switch blade 256, moving it from contact 258 to contact 259. A circuit is thereby established from transformer 34 through motor 2 l conductor 36, brush 26, commutator'tube 25, brush 29, conductor 4|, terminal 42, c0nductor l1c, term'mal 242a, conductor 2111), contact 259, blade 256, bracket 251, conductor, 251a terminal 238a, conductor 13c, terminal 38, conductor 31, terminal 36, back. ,to the transformer. Therefore, the motor will operate untilshaft 22 has been given a half-rotation and'insulation 25b appears under the brush 29. This operation is independent of the position of the thermostat andof the basement switch. Thus, if=the basement switch had been set at its on position it would have been unable to prevent the off operation just described, the internal circuit being complete from terminal 242a to terminal 238a merely through off contact 259 and contact blade 256. If now the basement switch is moved to the on posir tion, an on operation is not brought about since the on circuit through terminal 240a, conduc-i tor 215b, contact button 215, conductor 2151), and

limit switch is master over the basement switch. Thus, if the user should leave the basement switch ductor 261a, basement-switch arm 21], conductor 272a, contact 258, switch arm 256, conductor 251a, terminal 233a, conductor I30, terminal 38, conductor 31, terminal 36, to the other side .of the transformer secondary. If the room thermostat on the on position, it could not prevent an off operation upon excessive increase in temperanow moves to the off-call position, the lamp ture in the bonnet or stack which would reprewill be extinguished and the damper motor will sent a great fire hazard. Similarly, if the drafts be moved to the drafts-off position. have been turned off as a result of excessive If now the low limit switch is moved to on temperatures in the bonnet or stack, it-will not position the arm Z66 touches contact 268. Lamp be possible to overcome its safeguarding action 58 will be energized immediately through the folby moving the basement switch to the on posilowing circuit; from the transformer secondary tion. The reason for this result is that the cirthrough conductor 53, terminal 52, conductor 51, cuit is so arranged that the off circuit is delamp 5?), conductors 54 and b, terminal I5a, pendent only upon the high limit switch and is 15 conductor l5, terminal 2l5a, conductor 2l5b, conindependent of the basement switch and of the tact 268, contact arm 266, bracket 261., conductor thermostat. 261a, basement-switch arm 21!, conductor 212a, It will be noted, however, that the basement contact 258, switch arm 256, bracket 251, conswitch has mastery over .the low limit switch. ductor 251a, terminal 238a, conductor I30, termi- Thus, if the temperature in the bonnet or the nal 38, conductor 31, terminal 36 back to the stack is so low that the low limit switch is moved other side of the transformer secondary. At the to the on position (which may occur when insame time a circuit will be established through stallation takes place in a cold furnace), the inmotor 2! as follows: terminal 32, conductor 3!, stallation man may, in order to test the installamotor 2 l, conductor 30, brush 26, tube 25, brush tion, move the basement switch to the off posi- 21, conductor 39, terminal 40, conductor 150, tion and thereby secure an operation, irrespective terminal 240a, conductor 215b, contact 268, switch of the position of the room thermostat. arm 25%, conductor 267a,, basement-switch arm Assuming that the motor is in the position 27!, conductor 212a, contact 258, switch arm shown, drafts on, as a result of the operation of 256, conductor 257a, terminal 238a, conductor 130, the low limit switch, and that the basement terminal 33., conductor 31, terminal 36 to the switch is now moved to the off position, it will other side of the transformer secondary. This be noted that a circuit is established from the will cause the damper motor to operate to the transformer through the motor 2|, brush 26, condrafts on position. ductor 30, tube 25, brush 29, conductors M, ile, By following the circuit shown in Fig. 8, it 2111), contact button 214, lever 21!, conductor will be noted that the lamp 50 will always be 212a, on contact 258, blade 255, conductor 251a, energized whenever the damper motor is in the conductor I30, terminal 38, conductor 37, back drafts on position, whether this be the result to the transformer. This results in a half revoof the call of the room thermostat or as a result lution of the shaft 22 until insulation 25b moves of the call of the basement switch or as a result under brush ThuS, a rafts-off operationis' m of the call of the low limit switch. The eighteen completedin spite of the fact that the low limit possible conditions and the resultant action can switch is in on position. be seen from the following table:

R B t Limit switch Iany opcra- O Thern o stat star tits??? Lem Low Limit High Limit turned 1------ on oalL--. normalnormal (ofi call).-- normal (0ll'call) on- Dim while motor inns, thenbright. 2 off call. do do (10 off... Dim while motor runs, then out. 3 onca11..--. on calls-.. do d n11 Dim while motor runs, then bright. Oant turn 011? light at thermostat. do o Seme'as 3. do ofi Same as 2. (1 d0 d0 v 0. off c2111.- .l c d 14. a don I 'r1n ird do Do. '17.....' on call off call 011..- SamezasZ '18..- ofica1l ..c 'do "o l Do.

It will be noted "that the lamp 50 is connected to the thermostat and damper motor in the same way as in Figs. 1 and "7 and that when the parts are in the position shown in Fig. '8, the lamp will be'energized through the following circuit; from transformer secondary winding 33 through con ductor 53, terminal 52, conductor 5!, lamp 5'0, conductor 5-4, contact *M, bi-m'e'tal H, conductor terminal 130,, conductor 13, "terminal 213a, conductor-2 13b, contact 269, switch arm 266, con- That these results are obtained will be readily apparent to those skilled in this art by tracing the circuits shown in Fig. 8. It will be noted that the lamp always truly indicates the condition of the drafts whether as a result of the call of the room thermostat, the basement switch, or the limit switch. When the drafts are open the lamp is illuminated and when the drafts are closed the lamp isextinguis'hed.

Referring to Figs. 9, '10 and 11, the thermostat parts are designated by the same reference numerals as those used in Fig. 1. The numeral 300 designates a heat-supply controlling device of any type requiring a single circuit, viz., such as a solenoid valve for controlling gas or liquid fuel, or hot water or steam, or a relay for controlling the motor circuit of a stoker or oil burner. Said device is provided with two terminals 301 and 302. The transformer secondary 33 is connected to the terminal 301 via conductor 303 and to conductor 53 and its other side is connected to the conductor 13. The terminal 15a is connected to the terminal 302 via conductor 15.

In the system of Fig. 9 it will be seen that when, upon falling temperature, contact is made between 11 and 14, two parallel circuits will be established, (1) through lamp 50 and (2) through the device 300. The lamp 50 will, therefore, be

energized at all times when the device 300 is energized. 1

Referring to Fig. 10, the conductor 13, instead of connecting directly with winding 33, is connected to a contact 305 against which may bear a contact blade 306 actuated by the thermo-responsive element 301 which is connected through conductor 308 with the winding 33. This system will operate in the same manner as the system of Fig. 9 whenever contact exists between 305 and 306. However, if a certain limiting temperature is achieved, as in the bonnet of a hot-air furnace or the stack of any furnace (or if certain pres sure is achieved, assuming the element 301 to be pressure-responsive), the circuit is broken at 305 and 306 causing the lamp 50 to be extinguished and the device 300 to be de-energized.

The device of Fig. 11 is identical with that of Fig. 10 with the exception that a second temperature or pressure-responsive member 311 is provided having a contact member 316 co-operable upon drop in temperature or in pressure with contact 315 connected via conductor 310 with the conductor 15. Said member 311 is connected through conductor 319 with the conductor 308 and the winding 33.

In the system of Fig. 11 the temperatureresponsive element I 1 and, on occasion, the temperature-responsive element 301, controls energization of device 300 and simultaneously of the lamp 50. If, however, as in mild weather, the element 11 is satisfied for a sufliciently long time to permit the temperature of the bonnet or stack (or the pressure) to drop sufficiently far to cause element 316 to engage contact 315, the device 300 will be energized and simultaneously the lamp 50 illuminated, even though element 11 does not call for heat. Device 300 is energized through the circuit from winding 33 via conductor 319, element 316, contact 315, conductor 318, conductor 15, terminal 302, device 300, terminal 301, conductor 303, to the other side of the winding. Simultaneously, a circuit is completed via conductor 15, terminal 15a, conductor 15b, conductor 54, lamp 50, conductor 51, terminal 52, conductor 53, back to the winding 33.

It will be seen that according to the devices of Figs. 9, l and 11, the lamp 50 will always be illuminated when the device 300 is energized and at no other time. This is true in Fig. 11 whether such energization takes place as a result of a call by the thermostat 1114 or of the low limit switch 316-315. Likewise, if de-energization of device 300 occurs, the lamp 50 will be extinguished, whether such de-energization occurs because the room thermostat is satisfied or because the high limit switch of Figs. or 11 is 14 satisfied. Therefore, the lamp 50 will always truly indicate the condition of the device 300.

It will be noted that the construction shown and described will serve admirably to accomplish the objects stated above. It is to be understood, however, that the constructions disclosed above are intended merely as illustrative of the invention and not as limiting as various modifications therein may be made without departing from the invention as defined by a proper interpretation of the claims which follow.

I claim:

1. In a temperature control system of the type having a thermostat including a thermo-responsive switch, a combined high and low limit switch, a heat-supply controlling device, a plurality of conductors connecting said switch for controlling said heat-supply controlling device via said limit switch, andan electric source connected to for operating said heat-supply controlling device; the combination of a lamp so associated with said thermostat that heat therefrom, when energized, afiects said thermo-responsive switch and a conductor leading from one terminal of said lamp to said electric source, the other side of said lamp being connected to the other side of said electric source via said thermoresponsive switch and one of said plurality of conductors.

2. In a temperature control system of the type having a thermostat including a thermo-responsive single-pole double-throw switch, a singlepole double-throw limit switch, a heat-supply controlling device, a plurality of conductors connecting said switch for controlling said heatsupply controlling device via said limit switch, and an electric source connected to for operating said heat-supply controlling device; the combination of a lamp so associated with said thermostat that heat therefrom, when energized, afiects said thermo-responsive switch and a conductor leading from one terminal of said lamp to said electric source, the other side of said lamp being connected to the other side of said electric source via said thermo-responsive switch, one of said plurality of conductors and said limit switch.

3. In a temperature control system, a thermoresponsive switch, a high limit switch, a low limit switch, a heat-supply controlling device, an electric source, an electric heat source so associated with said thermo-responsive switch that heat therefrom, when energized, affects said thermoresponsive switch and conductors so interconnecting said switches, said electric source, said heat source and said controlling device that closing of either said thermo-responsive switch or said low limit switch will, when the high limit switch is closed, establish parallel circuits from said electric source, one circuit through said heat source and one circuit through said controlling device, and that opening of said high limit switch will break both of said parallel circuits irrespective of the setting of said thermoresponsive switch and said low limit switch.

4. In a temperature control system of the type having a thermostat including a thermo-responsive switch, a heat-supply controllin device, a plurality of conductors connecting said switch to said heat-supply controlling device, and an electric source connected to for operating said heat-supply controlling device; the combination of a lamp so associated with said thermostat that heat therefrom, when energized, affects said thermo-responsive switch and a conductor lead- 115 inafromone :terminalof said lamp to said elecric source, a manual switch associated with said heat-sup ly control-ling device so connected that when operated it causes said heat-supp1y controlling device to be operated by said electo said heat-supply controlling device, and an electric source connected to for operating said heat-supply controlling device; the combination of a supplemental heat source in heat conductive relation to said thermo-responsive switch and a .conductor leading from one terminal-of said heat source to said electric source, a manual switch associated with said heat-supply controlling device so connected that when operated it causes said heat-supply controlling device to be operated by said electric source to increased heat position and circuit means controlled by said heat-supply control means to energize said heat source when the control means has been thus operated to increased heat position, irre spective of the position of the thermo-responsive switch.

6. In a temperature control system of the type having a thermostat including a thermo-respon- .sive switch, a heat-supply controlling device, a plurality of conductors connecting said switch to said heat-supply controlling device, and an electric source connected to for operatin said heat-supply controlling device; the combination-of ;a lamp so associated with said thermostat that heat therefrom, when energized, affects said thermo-responsive switch and a conductor leading from one terminal of said lamp to said electric source, a manual switch associated with said heat-supply controlling device so connected that when operated to one position it causes said REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,583,496 Shafer May 4, 1926 1,835,307 Johnson Dec. 8, 1931 1,876,636 Dicke Sept. 13, 1932 1,981,251 Roth Nov. 20, 1934 2,110,192 Bellamy -1- Mar. 8, 1938 2,129,477 Parks Sept. 6, 1,938 2,164,352 Sargent July 4, 1939 2,300,839 Dicke .Nov. 3, 1942 2,301,383 Dillman Nov. 10, 1942 2,342,126 Dicke Feb. 22, 1944 2,402,177 Miller June 18, 1946 

